The present invention relates to industrial vehicles that include a hydraulic brake device and a hydraulic load handling device.
For example, forklifts have been known as industrial vehicles with hydraulic actuators. For example, refer to Japanese Laid-Open Patent Publication No. 2002-114499. In the forklift of Japanese Laid-Open Patent Publication No. 2002-114499, pressure for actuating a hydraulic actuator is accumulated in a hydraulic accumulator. The accumulated pressure is released to actuate the actuator. The hydraulic mechanism in the forklift of the above publication employs an open center type control valve, which connects the hydraulic pump and the oil tank when actuation of the load handling device is not instructed. Thus, even if actuation of the load handling device is not instructed, pressure can be accumulated in the hydraulic accumulator by driving the hydraulic pump.
Recently, to reduce variation in the speed of load handling devices between a case in which no load is being handled and a case in which a load of the maximum loading weight is being handled, closed center type control valves have started being employed in hydraulic mechanisms. A closed center type control valve is configured to disconnect the hydraulic pump and the load handling device from each other when actuation of the load handling device is not instructed. A hydraulic mechanism that employs a closed center type control valve has a pressure compensating valve. The pressure compensating valve compensates for the working pressure of the hydraulic cylinder that actuates the load handling device. The pressure compensating valve is configured to release the pressure by discharging hydraulic oil to the oil tank when the pressure in the hydraulic circuit exceeds the relief pressure. Thus, in a hydraulic mechanism that employs a closed center type control valve, even if the hydraulic pump is driven when actuation of the load handling device is not instructed, the pressure in the hydraulic circuit is released via the pressure compensating valve, and pressure cannot be accumulated in the hydraulic accumulator. Therefore, a configuration for accumulating pressure in a hydraulic accumulator must be considered in a hydraulic mechanism employing a closed center type control valve.